1. Field of the Invention
The present invention relates to a laser processing apparatus and a laser processing method for performing pattern processing on a transparent conductive film used for a transparent electrode on a multilayer thin film of an FPD (Flat Panel Display), a solar cell and the like. Particularly, the present invention relates to a laser processing apparatus and a laser processing method, as well as to a debris extraction mechanism and a debris extraction method for efficiently removing and extracting debris. The debris is particles and products generated during laser processing based on photochemical reaction (ablation), thermofusion or composite action thereof in which a surface of a processing object is irradiated with laser light from the lower side thereof.
2. Description of the Related Art
Resin materials are typically used as a resist material and a planarizing material in a process of manufacturing a flat panel display including a liquid crystal panel. A number of photolithography processes are performed when patterning and etching those resin materials. Hence, a huge facility investment may be required, and a large amount of chemical solution is used, which may cause damage to the environment. In order to solve these problems, there has been desired a technology of directly patterning materials by using laser light. When laser processing is performed in general, extraction of processing products called debris becomes a major issue. Here, the debris is products generated from a processed material that has absorbed and reacted to laser light and minute particles generated from the processed material. These products and particles are suspended and scattered in the air and then re-deposited on a substrate. Particularly, reaction products deposited on the substrate cause a defect in a finished product, because such reaction products are hardened due to the temperature drop when they are re-deposited on the substrate and a removal thereof is difficult even by scrubbing physically using a brush or the like.
In the field of fine processing which deals with the flat panel display including the liquid crystal panel, such re-deposition of particles (dust) definitely causes defects. Accordingly, a technology to extract debris may be required. A transparent conductive film is typically patterned into a desired shape by a photolithography method. For example, a transparent conductive film made of an ITO (Indium Tin Oxides) film, ZnO (Zinc Oxides) film or the like is vacuum-coated on a glass, plastic or silicon-wafer substrate and the like. Then, a resist layer is formed thereon and exposed by irradiation of light through a photomask having a predetermined pattern. The photomask pattern is transcribed onto the resist layer by performing development and post bake, then a portion of the transparent conductive film not covered with the resist is removed by wet etching, and the remaining resist layer is removed at the end so that the desired pattern of the transparent conductive film is obtained.
However, the photolithography process described above may need a large scale apparatus, such as a coater/developer, which causes a problem in view of the facility investment and the footprint. In addition, since a large amount of chemical solution such as a developing solution, is used, there is also caused an environmental preservation problem. Japanese Published Patent Application No. 2004-153171 discloses technology for directly processing a transparent conductive film by using laser light, with which a manufacturing process is simplified by omitting a photolithography process.
Japanese Published Patent Application No. 2004-188451 discloses a laser processing method and a laser processing apparatus, in which a surface of a processing object is irradiated with laser light, causing debris generated from a region irradiated with the laser to be deposited on an adsorption panel by a magnetic field. By doing so, there is obtained a laser processing method in which debris generated by laser processing is prevented from being re-deposited on the processed surface when the processing based on ablation or thermofusion is performed by irradiating the surface of the processing object with the laser light. According to the laser processing methods disclosed in the above-described Patent References, the processing object is irradiated with laser light from the upper side thereof. Therefore, debris from the processing object is scattered in all directions.
Further, Japanese Published Patent Application No. 2002-126890 discloses a debris extraction technology in which a duct for extracting dust, whose shape and distance from the processed surface has been studied, is provided in the case where laser light is used to perform the processing of drilling a metal plate used for an industrial purpose. Further, Japanese Published Patent Application No. 2000-317670 discloses a method of extracting debris by air flow while physically covering an area of an irradiated portion. Furthermore, Japanese Published Patent Application No. 09-271980 discloses a method of sucking debris in which the vicinity of an irradiated portion is made into a double structure using a kind of curtain.
Moreover, Japanese Published Patent Application No. 10-99978 discloses a method of reducing debris deposited onto a substrate. In this method, a fluid delivery apparatus blowing a gas onto a surface in the vicinity of a processed region and a suction duct sucking a fluid on the opposite side are provided. Then, debris is blown off the processed region and simultaneously sucked and removed.
FIG. 1 shows a configuration disclosed in the above-described Japanese Published Patent Application No. 10-99978. An apparatus shown in FIG. 1 is a laser processing apparatus for stamping a manufacturer's serial number on a glass substrate 5 arranged in part of a manufacturing process for preparing a predetermined product. In this manufacturing process, various coating processings and patternings are performed on the glass substrate 5 through a series of processes using a plurality of processing machines. This laser processing apparatus includes a processing table 20, a laser irradiation apparatus 22, a fluid feed apparatus 24, and a discharge apparatus 26. The processing table 20 moves in two directions parallel with a plane of the glass substrate mounted 5 to determine the position of a stamp region 21 where the manufacturer's serial number is stamped. The laser irradiation apparatus 22 stamps the manufacturer's serial number corresponding to the kind of the mounted glass substrate 5 onto the stamp region 21. The fluid feed apparatus 24 has a blow nozzle 23 for directing a fluid to the stamp region 21 of the glass substrate 5 mounted on the processing table 20. The discharge apparatus 26 has a suction duct 28 for sucking the fluid over the stamp region 21. Debris 7 generated by irradiating a black matrix 27 of the stamp region 21 with laser light 1a is removed by a processing using the laser light 1a emitted from a laser oscillator 1 through an objective lens 25 of the laser irradiation apparatus 22.
However, debris is intended to be extracted in those patent references to the extent of not affecting a human body. Hence, it is difficult to control and extract particle patterns in the order of several μm to several tens μm, which can be applied to processing of a fine device such as a transparent conductive film formed on a glass substrate of a liquid crystal panel.
Further, a reaction mechanism called ablation, as described above, may occur in the range of a wavelength of excimer lasers to be used as a laser source, for example. In the ablation processing, energy of the laser light is absorbed by a material to be processed, disintegrating the material without generating heat by disrupting chemical bonds that form a molecular frame. Consequently, it is said that less debris is generated. In addition, a simplified debris extraction method of only blowing a helium (He) gas, a nitrogen (N2) gas or the like is typically used. However, practically, there are not many cases in which the processing of fine devices can be performed only by the ablation of a photochemical reaction, but in most cases a composite process including a heat-affected process is used.
Further, a semiconductor-process-applied product, such as a liquid crystal panel, has a complicated film structure as a material thereof, and therefore a different phenomenon occurs compared with a single-layer film. When a plurality of process factors are thus mixed, the debris extraction becomes complicated, and it is necessary to analyze a debris generation mechanism in detail and to develop a debris extraction method suitable for each case. At present, a transparent conductive film is used as a transparent electrode of a multilayer film substrate for a flat display panel of a solar cell and the like. Also, a transparent conductive film is widely used as a transparent electrode in the field of electronic paper whose development has been promoted as a future display device, and the use thereof has been expanded. Further, since the competition for higher definition and lower costs of a display has become more intensive recently, a transparent conductive film of higher quality and higher productivity may also be required in manufacturing a display. Accordingly, the inventors of the present application recognize a necessity to analyze the debris generation mechanism in detail and to obtain a laser processing apparatus, a laser processing method, a debris extraction mechanism and a debris extraction method which are suitable for each case.